For example, a construction machine for performing excavating operations is generally equipped with two variable capacity type hydraulic pumps adapted to be driven by an engine in order to feed a pressurized hydraulic oil to hydraulic actuators in the form of hydraulic cylinders, hydraulic motors or the like.
A technology for varying horse powers to be absorbed by variable capacity type hydraulic pumps corresponding to a magnitude of load while maintaining a sum of the absorptive horse powers of the hydraulic pumps at a level corresponding to a predetermined value has been heretofore proposed (e.g., refer to Japanese Patent Application NO. 60841/1984).
The foregoing predetermined value is practically set to a value which represents a rated horse power derived from the engine.
With the prior technology as described above, in a case where one of the hydraulic pumps has a smaller absorptive horse power, the absorptive horse power allowable relative to the other hydraulic pump is enhanced correspondingly. This enables the rated horse power of the engine to be utilized effectively.
However, it has been found that the prior technology has the following drawback.
Specifically, since the absorptive horse powers of the respective hydraulic pumps are not individually monitored, optimum distribution of the absorptive horse powers relative to the respective hydraulic pumps sometimes fails to be carried out.
Another drawback of the prior technology is that a controlling operation is performed with a low accuracy, because the prior technology is practiced by employing mechanical components.
The present invention has been made with the foregoing background in mind and its object resides in providing an apparatus for controlling hydraulic pumps for a construction machine wherein distribution of horse powers to be absorbed by the hydraulic pumps can adequately be carried out with an excellent accuracy.